Lighter, Faster 250cc Motocrosser
The KX design philosophy – to put midlevel to expert riders on the top step of the podium – has not changed since the brand was launched over 40 years ago. The KX250F has a history of winning: in the extremely competitive 4-stroke 250cc class it is the racer with the most AMA Supercross and Motocross titles. Adding to its highly acclaimed engine and chassis performance, numerous industry firsts and advanced technology, the 2017 model offers a more powerful engine, a significantly lighter chassis, and slimmer ergonomics, making the new model the fastest KX250F yet. The new model gets around the track 1.6 seconds quicker* than its predecessor. *Kawasaki test rider on a 1’55s-lap course.
Key Features of the 2017 KX250F
- 4 position adjustable handlebar
- Separate Function front Fork (SFF) Type 2
- Oversized petal disc brakes
- Factory styling - graphics and finishes
- 2 position adjustable footpegs
- Uni-Trak rear suspension
- Next-level Power and Performance
- Downdraft-style intake routing
- 249cm³ liquid cooled, 4-stroke single with dual injectors
- Setting adjustable motocross ECU
- Slimmer and lighter aluminium perimeter frame
- Lightest in class
The KX design philosophy - to put mid-level to expert riders in the top step of the podium - has not changed since the brand was launched over 40 years ago. The KX250F is perhaps the motocross bike to put you out the front of the pack and keep you there.
Advanced Suspension Technology
Separate Function Front Fork (SFF) Type 2
The KX250F was the first mass-production motocrosser to feature Showa’s Separate Function front Fork (SFF), which separates damping and shock absorption duties:
- Left fork tube: damping assembly
- Right fork tube: spring
The configuration offers both smooth action and firm damping performance – a combination difficult to achieve with a conventional fork.
- Using large φ48 mm inner tubes contributes to greater fork rigidity, resulting in a more planted feel from the front wheel.
- With only one spring, the friction generated between the spring(s) and fork inner tube(s) is greatly reduced (approximately 25% less), resulting in extremely smooth action throughout the fork stroke.
- Being able to use larger damper pistons not only enables smoother action, it also makes firm damping performance possible.
- The large diameter fork tubes enable larger damper components.
Main piston diameter 30 mm
Sub-piston diameter 35 mm
With the larger components, the same damping force as the 47 mm SFF Type 1 can be achieved with a lower internal pressure. With the lower pressure, the 48 mm SFF Type 2 is even better equipped to offer both increased riding comfort and firmer damping performance.
For 2017, a lighter inner-tube design fine-tunes fork rigidity. Together with revised shim stack layout, revised oil level and firmer spring rate (9.6 N/mm >> 9.8 N/mm), the busy pitching effect over braking bumps is reduced, and cornering stability is increased while sharp turn-in is maintained. High-speed stability is of course uncompromised.
Race Ready Front Suspension
A super-hard titanium coating on the outer surface of the inner fork tubes helps prevent wear abrasion. The increased surface hardness of the dark navy blue coating also helps to prevent scratches and damage to the tubes. Because the surface remains smooth for a longer period, sliding friction (and stiction) is reduced and action is improved, contributing to a smoother ride. (The KX250F is the only motocrosser in its class to feature this race-ready coating standard.)
Removing the damper assembly from the right fork tube frees up space for a pre-load adjuster. Having a preload adjuster simplifies the task of setting the fork preload or front height. The racer friendly SFF Type 2 also facilitates other maintainence chores like adjusting damping and changing springs.
Race Ready Rear Suspension
The rear shock features dual compression adjustability, allowing high-speed and low-speed damping to be tuned separately. A self-lubricating anodised coating on the tank cylinder helps prevent wear abrasion, and reduces friction for smoother suspension action.
Revised valve settings contribute to improved ride feel and increased rear-end feedback. Lighter shock spring (care of thinner wire diameter, fewer coils and shorter length) offers 285 g in weight savings. Lower spring rate (53 N/mm >> 52 N/mm) contributes to the reduced pitching effect over braking bumps.
Uni-Trak rear suspension system mounts the suspension arm below the swingarm, allowing a longer rear suspension stroke. The longer stroke in turn allows more precise rear suspension tuning. Extensive rider testing was conducted to determine the ideal linkage ratios and rear shock absorber damping settings to achieve maximum rear wheel traction.
For 2017, a slimmer new frame is one of the many components contributing to the new KX250F’s trimmer form. Weighing over 1.5 kg less than its predecessor, the new model is quicker both in the straights and through the corners. Suspension settings for the high-spec SFF Type 2 front fork and Uni-Trak rear shock were adjusted to deliver greater stability over braking bumps and through corners. A slimmer, flatter rider interface further improves the adjustable racer-friendly ergonomics, helping racers to rider even faster.
Oversize New Petal Disc
Larger oversized 270mm front disc (up from 252mm) contributes to increased braking power and control.
The radical design front and rear petal discs offer strong braking performance, excellent competitive edge with high quality factory looks.
Bridged Box Bottom Piston Design
High-performance piston, featuring the same design used on our factory racers, contributes to strong performance at all rpm. A short skirt, reinforced external ribs and the use of a bridged-box bottom, featuring internal bracing, contributes to a light, strong piston design. Already the lightest piston in its class, revised design and strength optimisation save an additional 4 g, further reducing reciprocating weight and contributing to the engine’s increased performance. Piston pin is offset 0.25 mm, complementing the offset cylinder and reducing mechanical loss. Strength optimisation results in a lighter piston pin: weight decreases 2 g. Coating and striation on the piston outer surface ensure good wear resistance and oil retention for minimal sliding friction. A change from tin plating to a molybdenum coating reduces mechanical loss.
Easy engine tuning: DFI Setting Data Selection (3 map choices)
Adjusting engine settings to suit conditions has never been easier than with the KX’s FI couplers. Plug-and-play style system is quick, easy and stress-free. Instead of a single engine map, the ECU features three (four, counting the Launch Control Mode map). Initial settings for the three maps are: Standard (green), Hard (conditions)(black) and Soft (conditions)(white). Using provided FI couplers, riders are able to easily switch between the three maps to suit riding conditions. Plugging in each of the 4-pin couplers activates the corresponding engine map. (Plug is conveniently located on the right side of the head pipe for easy access without having to remove any parts.)
Each of the three maps can be reprogrammed using the optional KX FI Calibration Kit.
Precision engine tuning: KX FI Calibration Kit (Accessory)
The updated KX FI Calibration Kit features the handheld KX FI Calibration Controller, which enables expert riders to adjust engine characteristics (by rewriting actual data maps) to suit their preference. This simple tool can be used without a PC, simply by plugging into the engine’s ECU.
The KX FI Calibration Controller is handheld tool with a built in colour LCD screen. It comes with transfer and diagnostic cables, SD memory card, user manual and a carrying case.
Ask you Authorised Kawasaki Dealer for more information on this option.
The Holeshot Advantage: Launch Control Mode
The KX250F features a launch control system similar to that on our factory racers. With the simple press of a button, riders can activate a separate engine map designed to ensure efficient race starts in slippery conditions. The Launch Control Mode map retards ignition timing, allowing tyres to gain grip in low traction situations.
Launch Control Mode has the greatest effect within the first few seconds of releasing the clutch off the start. This is the most crucial time for the rider to get ahead of their rivals and line up the first corner.
To activate the Launch Control Mode riders depress the launch control button (for 2 seconds) located at the left handle. when activated the light next to the button will flash quickly to let the rider know it is on. Launch Control Mode works in 1st and 2nd gear. Once the rider shifts into 3rd gear, the system is automatically disengaged, switching back to the normal engine mapping.
43mm Throttle Body
43 mm throttle body is more compact and lightweight.
Designed specifically for motocrossers, the fuel injection system incorporates a small lightweight ECU and operates without a battery to further eliminate unnecessary weight. And of course, fuel injection eliminates the need to adjust engine settings to suit track and climate conditions
Adjustable Handlebar Position
A choice of four positions allows riders to tailor their riding position. Factory-style Renthal handlebar and pad come standard.
Upper triple clamp with two sets of handle mount slots and reversible handle mounts offers riders a choice of four handle positions to choose from: 25 mm FWD, 15 mm FWD, STD and 10 mm BK.
Powerful, High-Revving, Dual Injection Engine with Factory-Style Tuning
Tuned to best suit race-experienced riders, the 249 cm3 liquid-cooled, 4-stroke Single’s wide powerband focuses on high-rpm performance and extends way into the over-rev. Highly acclaimed for its high output and smooth power delivery, the 2017 model KX250F backs up its dual-injected power and race-inspired tuning and parts (like the high-performance bridged-box bottom piston) with downdraft-style intake routing and reduced mechanical loss (care of an offset cylinder and plateau honing, among other tweaks), resulting in a stronger lower end as well as a 1 kW increase in maximum engine output. As part of the development goal to become the lightest motocrosser in its class, changes to the engine group result in 0.8 kg in weight savings. Finally, a new accessory KX FI Controller enables map calibration without a PC.
The use of the world’s first dual injectors for a production motocrosser is a key component of the KX250F’s highly acclaimed fuel-injected performance. Tuned for high performance, its high-revving character is complemented by superb response. For 2017, downdraft-style intake routing and reduced mechanical loss further elevate engine output.
The downstream injector is used to ensure smooth instant response while the upstream injector is chanrged with providing power. As RPM and throttle postion increase, primary operation switches from the downstream injector to the upstream injector.
Both fuel injection are fine atomising injectors with 4 holes, dispersing spray particles with a droplet size of 120 µm from the upstream injector and 75 µm fro the downstream injector. The downstream injector's finer droplet size and wider spray angle contribute to stronger low-mid range power feeling, improved response and quicker acceleration.
Adjustable Footpeg Position
Riders can choose from two positions on the footpegs to suit their body size and personal preferences.
The adjustable brackets enable riders to lower the footpeg postion 5mm. In the lower position, centre of gravity is lowered as is the rider's point of view, adding to both the physical and psychological stability.
Matching the KX250F’s lighter weight, all-new KX450F-inspired minimalist bodywork makes the bike look more compact. Its shroud, fender and number plate designs ensure it is the sharpest looking bike in the paddock. Factory-style graphics further reflect the KX250F’s highly tuned performance, while new in-mould graphics give the design high durability. Green highlights on the suspension adjusters and engine oil cap and generator cover plugs contribute to a distinctive Kawasaki look.
- Kawasaki’s first in-mould graphics used on the shrouds result in an ultra-smooth surface and ensure the racy graphics are not easily damaged.
- Aggressive design of the new front fender adds to the racy looks and saves 50 g in weight. The rear fender’s sharp design contributes a further 70 g in weight savings.
- Rims are coated in black alumite1–just like our factory racers.
- Fork and rear shock adjusters have a green alumite1 finish like our U.S. factory racers.
- Embossed Kawasaki logo on the clutch cover made to appear as the contact from your riding boots wears off the paint.
- Green finish on the oil cap and the two plugs on the generator cover further contribute to factory looks.
- Embossed design on the clutch cover designed to gradually appear as contact from riding boots wears off the paint.
- Engine covers are finished in silver paint, further reinforcing the KX250F’s factory image.
1 Alumite: an anodic oxidation finishing treatment for aluminium resulting in a coloured, corrosion/scratch-resistant film coating.